Long Format Directory Listing 15x Slower in FreeBSD 5.x

[Kris Kennaway]

On Tue, Sep 13, 2005 at 11:55:55AM +1200, Nikolai Schupbach wrote:
> Hello,
> 
> We have been trying to migrate to FreeBSD 5.4 from an older 4.x release 
> for one of our busy mail servers. But we have encountered problems with 
> directory listings on 5.4.
> 
> Our /var/mail directory contains approximately 8,000 files doing a long 
> directory listing (ls -l) takes approximately 5 min and during this time 
> the CPU is running near 100%, on a FSBD 4 box the same directory 
> contents takes less than 20 seconds to list. Even on a directory with 
> 200 files, each file with a different owner, it will still take at least 
> 4-5 seconds to list. The problems only seems to occur when the directory 
> contains files from many different users. (as in /var/mail). If I chown 
> all the files in the /var/mail directory to a single user the directory 
> listing is near instant.
> 
> It appears it has something to do with 'ls' looking up the id's in the 
> password database, because if I instruct ls to display numeric IDs (ls 
> -ln), rather than converting to user and group names, the directory with 
> 8,000 files, with 8,000 different owners will list instantly.
> 
> The reason this concerns me so much is we are also having a problem with 
> our Washington IMAP / POP3 server on FBSD 5 using a lot of CPU while 
> operating on small and even 0 byte mailboxes, when there are approx five 
> or more concurrent POP3 or IMAP sessions. And I can't help thinking that 
> the two problems are related.
> 
> Does anyone have any ideas? Has anyone else noticed this problem? If I 
> can't resolve it I'm most likely going to revert to using 4.11, but I'd 
> really like to know what is going on. (and yes I'm using UFS_DIRHASH)

Sounds like the real problem is that you have >8000 users on your
machine and lookups are taking a long time.  There has been discussion
of this problem and how to solve it on freebsd-questions@ several
times..I think it involves making a minor change to pwd_mkdb and
rebuilding.  Please search the archives for that mailing list.

Kris
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